Meggitt VM600 User Manual

8 - 10 VM600 networking manual MAVM600-NET/E
Edition 9 - February 2018
MPC4 card
SETTING UP A MODBUS CONNECTION (CPUM SW VERSION 067 OR EARLIER)
Example:
A request to read one register at offset 55 (0x37 hexadecimal), containing a value of 4660
(0x1234 hexadecimal), gives the following:
See 8.4 Description of Modbus RTU protocol for examples of data.
Users familiar with Modbus RTU should note that the 'CRC-16' or 'LRC' check fields are not
needed in Modbus TCP. The TCP/IP and link layer (for example, Ethernet) checksum
mechanisms are used instead to verify accurate delivery of the data packet.
8.6 MPC4 card
The information is this section applies to the implementation of the Modbus software interface
for VM600 racks as used by CPUM cards running firmware version 067 or earlier.
Improved Modbus functionality is provided by CPUM cards running firmware version 071 or
later. See 9 Setting up a Modbus connection (CPUM firmware version 071 or later) for more
information.
8.6.1 Definition of registers
The register allocation is defined in files stored on the CPUM that are read when the VM600
rack is started up. These files are:
6
Unit identifier (previously 'slave address') – copied by server but
ignored
7 Modbus function code
8 onwards Data as required
Table 8-4: Modbus TCP prefix bytes (continued)
Bytes Function
TCP Modbus
Request : 00 00 00 00 00 06 0F 03 00 36 00 01
Response: 0000000000050F03021234
Byte : 01234567891011
mbcfg.2 For Modbus RTU communication through the RS-232 connector on the
front panel of the CPUM card. This uses a 9-pin D-type connector.
mbcfg.3 For Modbus RTU communication through the RS connector on the front
panel of the IOCN card. This uses a 6P6C (RJ11/RJ25) connector.
mbcfg.4 For Modbus RTU communication through the A connectors on the front
panel of the IOCN card. These use 6P6C (RJ11/RJ25) connectors.
mbcfg.5 For Modbus RTU communication through the B connectors on the front
panel of the IOCN card. These use 6P6C (RJ11/RJ25) connectors.
mbcfg.tcp For Modbus TCP communication through the 1 connector on the front
panel of the IOCN card for the primary network interface (ETH1) and
through the 2 connector on the front panel of the IOCN card for the
secondary network interface (ETH2), if installed. These use 8P8C (RJ45)
connectors.

Meggitt VM600 Specifications

General

Brand	Meggitt
Model	VM600
Category	Measuring Instruments
Language	English